Wireless power transmitting device and method of detecting foreign substances by wireless power transmitting device

ABSTRACT

A wireless power transmitting device according to an embodiment of the present specification transmits wireless power to a wireless power receiving device, and includes a power conversion circuit including a primary coil for transmitting the wireless power to the wireless power receiving device and a communication/control circuit for communicating with the wireless power receiving device and controlling the power conversion circuit, wherein, to detect foreign substances between the wireless power receiving device and the wireless power transmitting device, the communication/control circuit stops the transmission of the wireless power for a slot time, detects the foreign substances on the basis of a change in the voltage or current of the primary coil within the slot time, and sets the slot time to start from a point in time when the current of the primary coil is 0.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present specification relates to a wireless power transmitter fortransmitting wireless power to a wireless power receiver, a method fordetecting a foreign object between the wireless power receiver and thewireless power transmitter by the wireless power transmitter, and thelike.

Related Art

The wireless power transfer (or transmission) technology corresponds toa technology that may wirelessly transfer (or transmit) power between apower source and an electronic device. For example, by allowing thebattery of a wireless device, such as a smartphone or a tablet PC, andso on, to be recharged by simply loading the wireless device on awireless charging pad, the wireless power transfer technique may providemore outstanding mobility, convenience, and safety as compared to theconventional wired charging environment, which uses a wired chargingconnector. Apart from the wireless charging of wireless devices, thewireless power transfer technique is raising attention as a replacementfor the conventional wired power transfer environment in diverse fields,such as electric vehicles, Bluetooth earphones, 3D glasses, diversewearable devices, household (or home) electric appliances, furniture,underground facilities, buildings, medical equipment, robots, leisure,and so on.

The wireless power transfer (or transmission) method is also referred toas a contactless power transfer method, or a no point of contact powertransfer method, or a wireless charging method. A wireless powertransfer system may be configured of a wireless power transmittersupplying electric energy by using a wireless power transfer method, anda wireless power receiver receiving the electric energy being suppliedby the wireless power transmitter and supplying the receiving electricenergy to a receiver, such as a battery cell, and so on.

The wireless power transfer technique includes diverse methods, such asa method of transferring power by using magnetic coupling, a method oftransferring power by using radio frequency (RF), a method oftransferring power by using microwaves, and a method of transferringpower by using ultrasound (or ultrasonic waves). The method that isbased on magnetic coupling is categorized as a magnetic induction methodand a magnetic resonance method. The magnetic induction methodcorresponds to a method transmitting power by using electric currentsthat are induced to the coil of the receiver by a magnetic field, whichis generated from a coil battery cell of the transmitter, in accordancewith an electromagnetic coupling between a transmitting coil and areceiving coil. The magnetic resonance method is similar to the magneticinduction method in that is uses a magnetic field. However, the magneticresonance method is different from the magnetic induction method in thatenergy is transmitted due to a concentration of magnetic fields on botha transmitting end and a receiving end, which is caused by the generatedresonance.

SUMMARY OF THE DISCLOSURE

The technical problem of this specification is to provide a method formore accurately measuring a quality factor (Q factor) measured by awireless power transmitter temporarily stopping transmission of wirelesspower while transmitting wireless power to a wireless power receiver andto provide a foreign matter detection method using the same.

The technical tasks of the present specification are not limited to thetasks mentioned above, and other tasks not mentioned will be clearlyunderstood by those skilled in the art from the description below.

According to an embodiment of the present specification for solving theabove problems, a wireless power transmitter transmits a wireless powerto a wireless power receiver and comprises a power conversion circuitincluding a primary coil for transmitting the wireless power to thewireless power receiver and a communication/control circuitcommunicating with the wireless power receiver and controlling the powerconversion circuit, wherein the communication/control circuit isconfigured to stop a transmission of the wireless power during a slottime for detecting a foreign object between the wireless power receiverand the wireless power transmitter, and detect the foreign object basedon a change in voltage or current of the primary coil within the slottime, and wherein the slot time starts from a time point at which thecurrent of the primary coil becomes zero.

According to an embodiment of the present specification for solving theabove problems, a wireless power transmitter transmits a wireless powerto a wireless power receiver and comprises a power conversion circuitincluding a primary coil for transmitting the wireless power to thewireless power receiver and a communication/control circuitcommunicating with the wireless power receiver and controlling the powerconversion circuit, wherein the communication/control circuit isconfigured to stop a transmission of the wireless power during a slottime for detecting a foreign object between the wireless power receiverand the wireless power transmitter, and detect the foreign object basedon a change in voltage or current of the primary coil within the slottime, and wherein the communication/control circuit is configured todetect the foreign object based on the change in effective peak valuesobtained excluding a peak value of an initial section among peak valuesof current values or voltage values of the primary coil generated withinthe slot time.

According to an embodiment of the present specification for solving theabove problems, a method for detecting a foreign object is performed bya wireless power transmitter, wherein the wireless power transmitterincludes a primary coil for transmitting wireless power to a wirelesspower receiver, and comprises supplying power to the primary coil toprovide the wireless power to the wireless power receiver, blocking thepower supplied to the primary coil during a slot time and detecting theforeign object based on a change in voltage or current of the primarycoil within the slot time, wherein the slot time starts from a timepoint at which the current of the primary coil becomes zero.

Other specific details of this specification are included in thedetailed description and drawings.

While transmitting wireless power to the wireless power receiver, thewireless power transmitter temporarily stops transmission of thewireless power, and a quality factor (Q factor) to be measured can bemore accurately measured.

In addition, a foreign object existing between the wireless powertransmitter and the wireless power receiver may be more accuratelydetected using the more accurately measured quality coefficient.

The effect according to the present document is not limited by thecontents exemplified above, and more various effects are included in thepresent specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless power system (10) according toan exemplary embodiment of the present disclosure.

FIG. 2 is a block diagram of a wireless power system (10) according toanother exemplary embodiment of the present disclosure.

FIG. 3 a shows an exemplary embodiment of diverse electronic devicesadopting a wireless power transfer system.

FIG. 3 b shows an example of a WPC NDEF in a wireless power transfersystem.

FIG. 4 is a block diagram of a wireless power transfer system accordingto another exemplary embodiment of the present disclosure.

FIG. 5 is a state transition diagram for describing a wireless powertransfer procedure.

FIG. 6 shows a power control method according to an exemplary embodimentof the present disclosure.

FIG. 7 is a block diagram of a wireless power transmitter according toanother exemplary embodiment of the present disclosure.

FIG. 8 shows a wireless power receiver according to another exemplaryembodiment of the present disclosure.

FIG. 9 is a flowchart schematically illustrating a protocol of a pingphase according to an embodiment.

FIG. 10 is a flowchart schematically illustrating a protocol of aconfiguration phase according to an embodiment.

FIG. 1I is a diagram illustrating a message field of a configurationpacket (CFG) of a wireless power receiver according to an embodiment.

FIG. 12 is a flowchart schematically illustrating a protocol of anegotiation step or a renegotiation step according to an embodiment.

FIG. 13 is a diagram illustrating a message field of a capability packet(CAP) of a wireless power transmitter according to an embodiment.

FIG. 14 is a flowchart schematically illustrating a protocol of a powertransmission step according to an embodiment.

FIG. 15 is a schematic circuit diagram of a wireless power transmittersupporting a foreign object detection method by Slotted Q FOD.

FIG. 16 is a graph schematically showing a voltage attenuation waveformof a primary coil during a slot time.

FIG. 17 is a flowchart illustrating a foreign object detection methodaccording to an embodiment.

FIG. 18 is a diagram showing an example of data acquired in step S1504.

FIG. 19 is a diagram for explaining a method of obtaining effective peakvalues according to an exemplary embodiment.

FIG. 20 is a diagram for explaining a regression analysis methodaccording to an embodiment.

FIG. 21 is a flowchart for explaining a method of obtaining a referenceQ factor according to an embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

In this specification, “A or B” may refer to “only A”, “only B” or “bothA and B”. In other words, “A or B” in this specification may beinterpreted as “A and/or B”. For example, in this specification, “A, B,or C” may refer to “only A”, “only B”, “only C”, or any combination of“A, B and C”.

The slash (/) or comma used in this specification may refer to “and/or”.For example, “A/B” may refer to “A and/or B”. Accordingly. “A/B” mayrefer to “only A”, “only B”, or “both A and B”. For example, “A, B. C”may refer to “A. B. or C”.

In this specification, “at least one of A and B” may refer to “only A”,“only B”, or “both A and B”. In addition, in this specification, theexpression of “at least one of A or B” or “at least one of A and/or B”may be interpreted to be the same as “at least one of A and B”.

Also, in this specification, “at least one of A, B and C” may refer to“only A”, “only B”, “only C”, or “any combination of A, B and C”. Also,“at least one of A, B or C” or “at least one of A, B and/or C” may referto “at least one of A. B and C”.

In addition, parentheses used in the present specification may refer to“for example”. Specifically, when indicated as “control information(PDCCH)”, “PDCCH” may be proposed as an example of “controlinformation”. In other words, “control information” in thisspecification is not limited to “PDCCH”, and “PDDCH” may be proposed asan example of “control information”. In addition, even when indicated as“control information (i.e., PDCCH)”, “PDCCH” may be proposed as anexample of “control information”.

In the present specification, technical features that are individuallydescribed in one drawing may be individually or simultaneouslyimplemented. The term “wireless power”, which will hereinafter be usedin this specification, will be used to refer to an arbitrary form ofenergy that is related to an electric field, a magnetic field, and anelectromagnetic field, which is transferred (or transmitted) from awireless power transmitter to a wireless power receiver without usingany physical electromagnetic conductors. The wireless power may also bereferred to as a wireless power signal, and this may refer to anoscillating magnetic flux that is enclosed by a primary coil and asecondary coil. For example, power conversion for wirelessly chargingdevices including mobile phones, cordless phones, iPods, MP3 players,headsets, and so on, within the system will be described in thisspecification. Generally, the basic principle of the wireless powertransfer technique includes, for example, all of a method oftransferring power by using magnetic coupling, a method of transferringpower by using radio frequency (RF), a method of transferring power byusing microwaves, and a method of transferring power by using ultrasound(or ultrasonic waves).

FIG. 1 is a block diagram of a wireless power system (10) according toan exemplary embodiment of the present disclosure.

Referring to FIG. 1 , the wireless power system (10) include a wirelesspower transmitter (100) and a wireless power receiver (200).

The wireless power transmitter (100) is supplied with power from anexternal power source (S) and generates a magnetic field. The wirelesspower receiver (200) generates electric currents by using the generatedmagnetic field, thereby being capable of wirelessly receiving power.

Additionally, in the wireless power system (10), the wireless powertransmitter (100) and the wireless power receiver (200) may transceive(transmit and/or receive) diverse information that is required for thewireless power transfer. Herein, communication between the wirelesspower transmitter (100) and the wireless power receiver (200) may beperformed (or established) in accordance with any one of an in-bandcommunication, which uses a magnetic field that is used for the wirelesspower transfer (or transmission), and an out-band communication, whichuses a separate communication carrier. Out-band communication may alsobe referred to as out-of-band communication. Hereinafter, out-bandcommunication will be largely described. Examples of out-bandcommunication may include NFC, Bluetooth, Bluetooth low energy (BLE),and the like.

Herein, the wireless power transmitter (100) may be provided as a fixedtype or a mobile (or portable) type. Examples of the fixed transmittertype may include an embedded type, which is embedded in in-door ceilingsor wall surfaces or embedded in furniture, such as tables, an implantedtype, which is installed in out-door parking lots, bus stops, subwaystations, and so on, or being installed in means of transportation, suchas vehicles or trains. The mobile (or portable) type wireless powertransmitter (100) may be implemented as a part of another device, suchas a mobile device having a portable size or weight or a cover of alaptop computer, and so on.

Additionally, the wireless power receiver (200) should be interpreted asa comprehensive concept including diverse home appliances and devicesthat are operated by being wirelessly supplied with power instead ofdiverse electronic devices being equipped with a battery and a powercable. Typical examples of the wireless power receiver (200) may includeportable terminals, cellular phones, smartphones, personal digitalassistants (PDAs), portable media players (PDPs), Wibro terminals,tablet PCs, phablet, laptop computers, digital cameras, navigationterminals, television, electronic vehicles (EVs), and so on.

FIG. 2 is a block diagram of a wireless power system (10) according toanother exemplary embodiment of the present disclosure.

Referring to FIG. 2 , in the wireless power system (10), one wirelesspower receiver (200) or a plurality of wireless power receivers mayexist. Although it is shown in FIG. 1 that the wireless powertransmitter (100) and the wireless power receiver (200) send and receivepower to and from one another in a one-to-one correspondence (orrelationship), as shown in FIG. 2 , it is also possible for one wirelesspower transmitter (100) to simultaneously transfer power to multiplewireless power receivers (200-1, 200-2, . . . , 200-M). Mostparticularly, in case the wireless power transfer (or transmission) isperformed by using a magnetic resonance method, one wireless powertransmitter (100) may transfer power to multiple wireless powerreceivers (200-1, 200-2, . . . , 200-M) by using a synchronizedtransport (or transfer) method or a time-division transport (ortransfer) method.

Additionally, although it is shown in FIG. 1 that the wireless powertransmitter (100) directly transfers (or transmits) power to thewireless power receiver (200), the wireless power system (10) may alsobe equipped with a separate wireless power transceiver, such as a relayor repeater, for increasing a wireless power transport distance betweenthe wireless power transmitter (100) and the wireless power receiver(200). In this case, power is delivered to the wireless powertransceiver from the wireless power transmitter (100), and, then, thewireless power transceiver may transfer the received power to thewireless power receiver (200).

Hereinafter, the terms wireless power receiver, power receiver, andreceiver, which are mentioned in this specification, will refer to thewireless power receiver (200). Also, the terms wireless powertransmitter, power transmitter, and transmitter, which are mentioned inthis specification, will refer to the wireless power transmitter (100).

FIG. 3 a shows an exemplary embodiment of diverse electronic devicesadopting a wireless power transfer system.

As shown in FIG. 3 a , the electronic devices included in the wirelesspower transfer system are sorted in accordance with the amount oftransmitted power and the amount of received power. Referring to FIG. 3, wearable devices, such as smart watches, smart glasses, head mounteddisplays (HMDs), smart rings, and so on, and mobile electronic devices(or portable electronic devices), such as earphones, remote controllers,smartphones, PDAs, tablet PCs, and so on, may adopt a low-power(approximately 5 W or less or approximately 20 W or less) wirelesscharging method.

Small-sized/Mid-sized electronic devices, such as laptop computers,robot vacuum cleaners, TV receivers, audio devices, vacuum cleaners,monitors, and so on, may adopt a mid-power (approximately 50 W or lessor approximately 200 W or less) wireless charging method. Kitchenappliances, such as mixers, microwave ovens, electric rice cookers, andso on, and personal transportation devices (or other electric devices ormeans of transportation), such as powered wheelchairs, powered kickscooters, powered bicycles, electric cars, and so on may adopt ahigh-power (approximately 2 kW or less or approximately 22 kW or less)wireless charging method.

The electric devices or means of transportation, which are describedabove (or shown in FIG. 1 ) may each include a wireless power receiver,which will hereinafter be described in detail. Therefore, theabove-described electric devices or means of transportation may becharged (or recharged) by wirelessly receiving power from a wirelesspower transmitter.

Hereinafter, although the present disclosure will be described based ona mobile device adopting the wireless power charging method, this ismerely exemplary. And, therefore, it shall be understood that thewireless charging method according to the present disclosure may beapplied to diverse electronic devices.

A standard for the wireless power transfer (or transmission) includes awireless power consortium (WPC), an air fuel alliance (AFA), and a powermatters alliance (PMA).

The WPC standard defines a baseline power profile (BPP) and an extendedpower profile (EPP). The BPP is related to a wireless power transmitterand a wireless power receiver supporting a power transfer of 5 W, andthe EPP is related to a wireless power transmitter and a wireless powerreceiver supporting the transfer of a power range greater than 5 W andless than 30 W.

Diverse wireless power transmitters and wireless power receivers eachusing a different power level may be covered by each standard and may besorted by different power classes or categories.

For example, the WPC may categorize (or sort) the wireless powertransmitters and the wireless power receivers as PC-1, PC0, PC1, andPC2, and the WPC may provide a standard document (or specification) foreach power class (PC). The PC-1 standard relates to wireless powertransmitters and receivers providing a guaranteed power of less than 5W. The application of PC-1 includes wearable devices, such as smartwatches.

The PC0 standard relates to wireless power transmitters and receiversproviding a guaranteed power of 5 W. The PC0 standard includes an EPPhaving a guaranteed power ranges that extends to 30 W. Although in-band(IB) communication corresponds to a mandatory communication protocol ofPC0, out-of-band (OB) communication that is used as an optional backupchannel may also be used for PC0. The wireless power receiver may beidentified by setting up an OB flag, which indicates whether or not theOB is supported, within a configuration packet. A wireless powertransmitter supporting the OB may enter an OB handover phase bytransmitting a bit-pattern for an OB handover as a response to theconfiguration packet. The response to the configuration packet maycorrespond to an NAK, an ND, or an 8-bit pattern that is newly defined.The application of the PC0 includes smartphones.

The PC1 standard relates to wireless power transmitters and receiversproviding a guaranteed power ranging from 30 W to 150 W. OB correspondsto a mandatory communication channel for PC1, and IB is used forinitialization and link establishment to OB. The wireless powertransmitter may enter an OB handover phase by transmitting a bit-patternfor an OB handover as a response to the configuration packet. Theapplication of the PC1 includes laptop computers or power tools.

The PC2 standard relates to wireless power transmitters and receiversproviding a guaranteed power ranging from 200 W to 2 kW, and itsapplication includes kitchen appliances.

As described above, the PCs may be differentiated in accordance with therespective power levels. And, information on whether or not thecompatibility between the same PCs is supported may be optional ormandatory. Herein, the compatibility between the same PCs indicates thatpower transfer/reception between the same PCs is possible. For example,in case a wireless power transmitter corresponding to PC x is capable ofperforming charging of a wireless power receiver having the same PC x,it may be understood that compatibility is maintained between the samePCs. Similarly, compatibility between different PCs may also besupported. Herein, the compatibility between different PCs indicatesthat power transfer/reception between different PCs is also possible.For example, in case a wireless power transmitter corresponding to PC xis capable of performing charging of a wireless power receiver having PCy, it may be understood that compatibility is maintained between thedifferent PCs.

The support of compatibility between PCs corresponds to an extremelyimportant issue in the aspect of user experience and establishment ofinfrastructure. Herein, however, diverse problems, which will bedescribed below, exist in maintaining the compatibility between PCs.

In case of the compatibility between the same PCs, for example, in caseof a wireless power receiver using a lap-top charging method, whereinstable charging is possible only when power is continuously transferred,even if its respective wireless power transmitter has the same PC, itmay be difficult for the corresponding wireless power receiver to stablyreceive power from a wireless power transmitter of the power toolmethod, which transfers power non-continuously. Additionally, in case ofthe compatibility between different PCs, for example, in case a wirelesspower transmitter having a minimum guaranteed power of 200 W transferspower to a wireless power receiver having a maximum guaranteed power of5 W, the corresponding wireless power receiver may be damaged due to anovervoltage. As a result, it may be inappropriate (or difficult) to usethe PS as an index/reference standard representing/indicating thecompatibility.

Wireless power transmitters and receivers may provide a very convenientuser experience and interface (UX/UI). That is, a smart wirelesscharging service may be provided, and the smart wireless chargingservice may be implemented based on a UX/UI of a smartphone including awireless power transmitter. For these applications, an interface betweena processor of a smartphone and a wireless charging receiver allows for“drop and play” two-way communication between the wireless powertransmitter and the wireless power receiver.

Hereinafter, ‘profiles’ will be newly defined based on indexes/referencestandards representing/indicating the compatibility. More specifically,it may be understood that by maintaining compatibility between wirelesspower transmitters and receivers having the same ‘profile’, stable powertransfer/reception may be performed, and that power transfer/receptionbetween wireless power transmitters and receivers having different‘profiles’ cannot be performed. The ‘profiles’ may be defined inaccordance with whether or not compatibility is possible and/or theapplication regardless of (or independent from) the power class.

For example, the profile may be sorted into 3 different categories, suchas i) Mobile, ii) Power tool and iii) Kitchen.

For another example, the profile may be sorted into 4 differentcategories, such as i) Mobile, ii) Power tool, iii) Kitchen, and iv)Wearable.

In case of the ‘Mobile’ profile, the PC may be defined as PC0 and/orPC1, the communication protocol/method may be defined as IB and OBcommunication, and the operation frequency may be defined as 87 to 205kHz, and smartphones, laptop computers, and so on, may exist as theexemplary application.

In case of the ‘Power tool’ profile, the PC may be defined as PC1, thecommunication protocol/method may be defined as IB communication, andthe operation frequency may be defined as 87 to 145 kHz, and powertools, and so on, may exist as the exemplary application.

In case of the ‘Kitchen’ profile, the PC may be defined as PC2, thecommunication protocol/method may be defined as NFC-based communication,and the operation frequency may be defined as less than 100 kHz, andkitchen/home appliances, and so on, may exist as the exemplaryapplication.

In the case of power tools and kitchen profiles, NFC communication maybe used between the wireless power transmitter and the wireless powerreceiver. The wireless power transmitter and the wireless power receivermay confirm that they are NFC devices with each other by exchanging WPCNFC data exchange profile format (NDEF).

FIG. 3 b shows an example of a WPC NDEF in a wireless power transfersystem.

Referring to FIG. 3 b , the WPC NDEF may include, for example, anapplication profile field (e.g., 1B), a version field (e.g., 1B), andprofile specific data (e.g., 1B). The application profile fieldindicates whether the corresponding device is i) mobile and computing,ii) power tool, and iii) kitchen, and an upper nibble in the versionfield indicates a major version and a lower nibble indicates a minorversion. In addition, profile-specific data defines content for thekitchen.

In case of the ‘Wearable’ profile, the PC may be defined as PC-1, thecommunication protocol/method may be defined as IB communication, andthe operation frequency may be defined as 87 to 205 kHz, and wearabledevices that are worn by the users, and so on, may exist as theexemplary application.

It may be mandatory to maintain compatibility between the same profiles,and it may be optional to maintain compatibility between differentprofiles.

The above-described profiles (Mobile profile, Power tool profile,Kitchen profile, and Wearable profile) may be generalized and expressedas first to nth profile, and a new profile may be added/replaced inaccordance with the WPC standard and the exemplary embodiment.

In case the profile is defined as described above, the wireless powertransmitter may optionally perform power transfer only to the wirelesspower receiving corresponding to the same profile as the wireless powertransmitter, thereby being capable of performing a more stable powertransfer. Additionally, since the load (or burden) of the wireless powertransmitter may be reduced and power transfer is not attempted to awireless power receiver for which compatibility is not possible, therisk of damage in the wireless power receiver may be reduced.

PC1 of the ‘Mobile’ profile may be defined by being derived from anoptional extension, such as OB, based on PC0. And, the ‘Power tool’profile may be defined as a simply modified version of the PC1 ‘ Mobile’profile. Additionally, up until now, although the profiles have beendefined for the purpose of maintaining compatibility between the sameprofiles, in the future, the technology may be evolved to a level ofmaintaining compatibility between different profiles. The wireless powertransmitter ortho wireless power receiver may notify (or announce) itsprofile to its counterpart by using diverse methods.

In the AFA standard, the wireless power transmitter is referred to as apower transmitting unit (PTU), and the wireless power receiver isreferred to as a power receiving unit (PRU). And, the PTU is categorizedto multiple classes, as shown in Table 1, and the PRU is categorized tomultiple classes, as shown in Table 2.

TABLE 1 Minimum value for Minimum category a maximum number of PTUP_(TX) _(—) _(IN) _(—) _(MAX) support requirement supported devicesClass 1 2 W 1x Category 1 1x Category 1 Class 2 10 W 1x Category 3 2xCategory 2 Class 3 16 W 1x Category 4 2x Category 3 Class 4 33 W 1xCategory 5 3x Category 3 Class 5 50 W 1x Category 6 4x Category 3 Class6 70 W 1x Category 7 5x Category 3

TABLE 2 PRU P_(RX) _(—) _(OUT) _(—) _(MAX′) Exemplary applicationCategory 1 TBD Bluetooth headset Category 2 3.5 W Feature phone Category3 6.5 W Smartphone Category 4 13 W Tablet PC, Phablet Category 5 25 WSmall form factor laptop Category 6 37.5 W General laptop Category 7 50W Home appliance

As shown in Table 1, a maximum output power capability of Class n PTUmay be equal to or greater than the P_(TX_IN_MAX) of the correspondingclass. The PRU cannot draw a power that is higher than the power levelspecified in the corresponding category.

FIG. 4 is a block diagram of a wireless power transfer system accordingto another exemplary embodiment of the present disclosure.

Referring to FIG. 4 , the wireless power transfer system (10) includes amobile device (450), which wirelessly receives power, and a base station(400), which wirelessly transmits power.

As a device providing induction power or resonance power, the basestation (400) may include at least one of a wireless power transmitter(100) and a system unit (405). The wireless power transmitter (100) maytransmit induction power or resonance power and may control thetransmission. The wireless power transmitter (100) may include a powerconversion unit (110) converting electric energy to a power signal bygenerating a magnetic field through a primary coil (or primary coils),and a communications & control unit (120) controlling the communicationand power transfer between the wireless power receiver (200) in order totransfer power at an appropriate (or suitable) level. The system unit(405) may perform input power provisioning, controlling of multiplewireless power transmitters, and other operation controls of the basestation (400), such as user interface control.

The primary coil may generate an electromagnetic field by using analternating current power (or voltage or current). The primary coil issupplied with an alternating current power (or voltage or current) of aspecific frequency, which is being outputted from the power conversionunit (110). And, accordingly, the primary coil may generate a magneticfield of the specific frequency. The magnetic field may be generated ina non-radial shape or a radial shape. And, the wireless power receiver(200) receives the generated magnetic field and then generates anelectric current. In other words, the primary coil wirelessly transmitspower.

In the magnetic induction method, a primary coil and a secondary coilmay have randomly appropriate shapes. For example, the primary coil andthe secondary coil may correspond to copper wire being wound around ahigh-permeability formation, such as ferrite or a non-crystalline metal.The primary coil may also be referred to as a transmitting coil, aprimary core, a primary winding, a primary loop antenna, and so on.Meanwhile, the secondary coil may also be referred to as a receivingcoil, a secondary core, a secondary winding, a secondary loop antenna, apickup antenna, and so on.

In case of using the magnetic resonance method, the primary coil and thesecondary coil may each be provided in the form of a primary resonanceantenna and a secondary resonance antenna. The resonance antenna mayhave a resonance structure including a coil and a capacitor. At thispoint, the resonance frequency of the resonance antenna may bedetermined by the inductance of the coil and a capacitance of thecapacitor. Herein, the coil may be formed to have a loop shape. And, acore may be placed inside the loop. The core may include a physicalcore, such as a ferrite core, or an air core.

The energy transmission (or transfer) between the primary resonanceantenna and the second resonance antenna may be performed by a resonancephenomenon occurring in the magnetic field. When a near fieldcorresponding to a resonance frequency occurs in a resonance antenna,and in case another resonance antenna exists near the correspondingresonance antenna, the resonance phenomenon refers to a highly efficientenergy transfer occurring between the two resonance antennas that arecoupled with one another. When a magnetic field corresponding to theresonance frequency is generated between the primary resonance antennaand the secondary resonance antenna, the primary resonance antenna andthe secondary resonance antenna resonate with one another. And,accordingly, in a general case, the magnetic field is focused toward thesecond resonance antenna at a higher efficiency as compared to a casewhere the magnetic field that is generated from the primary antenna isradiated to a free space. And, therefore, energy may be transferred tothe second resonance antenna from the first resonance antenna at a highefficiency. The magnetic induction method may be implemented similarlyto the magnetic resonance method. However, in this case, the frequencyof the magnetic field is not required to be a resonance frequency.Nevertheless, in the magnetic induction method, the loops configuringthe primary coil and the secondary coil are required to match oneanother, and the distance between the loops should be very close-ranged.

Although it is not shown in the drawing, the wireless power transmitter(100) may further include a communication antenna. The communicationantenna may transmit and/or receive a communication signal by using acommunication carrier apart from the magnetic field communication. Forexample, the communication antenna may transmit and/or receivecommunication signals corresponding to Wi-Fi, Bluetooth, Bluetooth LE,ZigBee, NFC, and so on.

The communications & control unit (120) may transmit and/or receiveinformation to and from the wireless power receiver (200). Thecommunications & control unit (120) may include at least one of an IBcommunication module and an OB communication module.

The IB communication module may transmit and/or receive information byusing a magnetic wave, which uses a specific frequency as its centerfrequency. For example, the communications & control unit (120) mayperform in-band (IB) communication by transmitting communicationinformation on the operating frequency of wireless power transferthrough the primary coil or by receiving communication information onthe operating frequency through the primary coil. At this point, thecommunications & control unit (120) may load information in the magneticwave or may interpret the information that is carried by the magneticwave by using a modulation scheme, such as binary phase shift keying(BPSK), Frequency Shift Keying (FSK) or amplitude shift keying (ASK),and so on, or a coding scheme, such as Manchester coding ornon-return-to-zero level (NZR-L) coding, and so on. By using theabove-described IB communication, the communications & control unit(120) may transmit and/or receive information to distances of up toseveral meters at a data transmission rate of several kbps.

The OB communication module may also perform out-of-band communicationthrough a communication antenna. For example, the communications &control unit (120) may be provided to a near field communication module.Examples of the near field communication module may includecommunication modules, such as Wi-Fi, Bluetooth, Bluetooth LE, ZigBee,NFC, and so on.

The communications & control unit (120) may control the overalloperations of the wireless power transmitter (100). The communications &control unit (120) may perform calculation and processing of diverseinformation and may also control each configuration element of thewireless power transmitter (100).

The communications & control unit (120) may be implemented in a computeror a similar device as hardware, software, or a combination of the same.When implemented in the form of hardware, the communications & controlunit (120) may be provided as an electronic circuit performing controlfunctions by processing electrical signals. And, when implemented in theform of software, the communications & control unit (120) may beprovided as a program that operates the communications & control unit(120).

By controlling the operating point, the communications & control unit(120) may control the transmitted power. The operating point that isbeing controlled may correspond to a combination of a frequency (orphase), a duty cycle, a duty ratio, and a voltage amplitude. Thecommunications & control unit (120) may control the transmitted power byadjusting any one of the frequency (or phase), the duty cycle, the dutyratio, and the voltage amplitude. Additionally, the wireless powertransmitter (100) may supply a consistent level of power, and thewireless power receiver (200) may control the level of received power bycontrolling the resonance frequency.

The mobile device (450) includes a wireless power receiver (200)receiving wireless power through a secondary coil, and a load (455)receiving and storing the power that is received by the wireless powerreceiver (200) and supplying the received power to the device.

The wireless power receiver (200) may include a power pick-up unit (210)and a communications & control unit (220). The power pick-up unit (210)may receive wireless power through the secondary coil and may convertthe received wireless power to electric energy. The power pick-up unit(210) rectifies the alternating current (AC) signal, which is receivedthrough the secondary coil, and converts the rectified signal to adirect current (DC) signal. The communications & control unit (220) maycontrol the transmission and reception of the wireless power (transferand reception of power).

The secondary coil may receive wireless power that is being transmittedfrom the wireless power transmitter (100). The secondary coil mayreceive power by using the magnetic field that is generated in theprimary coil. Herein, in case the specific frequency corresponds aresonance frequency, magnetic resonance may occur between the primarycoil and the secondary coil, thereby allowing power to be transferredwith greater efficiency.

Although it is not shown in FIG. 4 , the communications & control unit(220) may further include a communication antenna. The communicationantenna may transmit and/or receive a communication signal by using acommunication carrier apart from the magnetic field communication. Forexample, the communication antenna may transmit and/or receivecommunication signals corresponding to Wi-Fi, Bluetooth, Bluetooth LE,ZigBee, NFC, and so on.

The communications & control unit (220) may transmit and/or receiveinformation to and from the wireless power transmitter (100). Thecommunications & control unit (220) may include at least one of an IBcommunication module and an OB communication module.

The IB communication module may transmit and/or receive information byusing a magnetic wave, which uses a specific frequency as its centerfrequency. For example, the communications & control unit (220) mayperform IB communication by loading information in the magnetic wave andby transmitting the information through the secondary coil or byreceiving a magnetic wave carrying information through the secondarycoil. At this point, the communications & control unit (120) may loadinformation in the magnetic wave or may interpret the information thatis carried by the magnetic wave by using a modulation scheme, such asbinary phase shift keying (BPSK), Frequency Shift Keying (FSK) oramplitude shift keying (ASK), and so on, or a coding scheme, such asManchester coding or non-return-to-zero level (NZR-L) coding, and so on.By using the above-described IB communication, the communications &control unit (220) may transmit and/or receive information to distancesof up to several meters at a data transmission rate of several kbps.

The OB communication module may also perform out-of-band communicationthrough a communication antenna. For example, the communications &control unit (220) may be provided to a near field communication module.

Examples of the near field communication module may includecommunication modules, such as Wi-Fi, Bluetooth, Bluetooth LE, ZigBee,NFC, and so on.

The communications & control unit (220) may control the overalloperations of the wireless power receiver (200). The communications &control unit (220) may perform calculation and processing of diverseinformation and may also control each configuration element of thewireless power receiver (200).

The communications & control unit (220) may be implemented in a computeror a similar device as hardware, software, or a combination of the same.When implemented in the form of hardware, the communications & controlunit (220) may be provided as an electronic circuit performing controlfunctions by processing electrical signals. And, when implemented in theform of software, the communications & control unit (220) may beprovided as a program that operates the communications & control unit(220).

Hereinafter, the coil or coil unit includes a coil and at least onedevice being approximate to the coil, and the coil or coil unit may alsobe referred to as a coil assembly, a coil cell, or a cell.

FIG. 5 is a state transition diagram for describing a wireless powertransfer procedure.

Referring to FIG. 5 , the power transfer (or transfer) from the wirelesspower transmitter to the wireless power receiver according to anexemplary embodiment of the present disclosure may be broadly dividedinto a selection phase (510), a ping phase (520), an identification andconfiguration phase (530), a negotiation phase (540), a calibrationphase (550), a power transfer phase (560), and a renegotiation phase(570).

If a specific error or a specific event is detected when the powertransfer is initiated or while maintaining the power transfer, theselection phase (510) may include a shifting phase (or step)—referencenumerals S502, S504, S508, S510, and S512. Herein, the specific error orspecific event will be specified in the following description.Additionally, during the selection phase (510), the wireless powertransmitter may monitor whether or not an object exists on an interfacesurface. If the wireless power transmitter detects that an object isplaced on the interface surface, the process step may be shifted to theping phase (520). During the selection phase (510), the wireless powertransmitter may transmit an analog ping having a power signal(or apulse) corresponding to an extremely short duration, and may detectwhether or not an object exists within an active area of the interfacesurface based on a current change in the transmitting coil or theprimary coil.

In case an object is sensed (or detected) in the selection phase (510),the wireless power transmitter may measure a quality factor of awireless power resonance circuit (e.g., power transfer coil and/orresonance capacitor). According to the exemplary embodiment of thepresent disclosure, during the selection phase (510), the wireless powertransmitter may measure the quality factor in order to determine whetheror not a foreign object exists in the charging area along with thewireless power receiver. In the coil that is provided in the wirelesspower transmitter, inductance and/or components of the series resistancemay be reduced due to a change in the environment, and, due to suchdecrease, a value of the quality factor may also be decreased. In orderto determine the presence or absence of a foreign object by using themeasured quality factor value, the wireless power transmitter mayreceive from the wireless power receiver a reference quality factorvalue, which is measured in advance in a state where no foreign objectis placed within the charging area. The wireless power transmitter maydetermine the presence or absence of a foreign object by comparing themeasured quality factor value with the reference quality factor value,which is received during the negotiation phase (540). However, in caseof a wireless power receiver having a low reference quality factorvalue—e.g., depending upon its type, purpose, characteristics, and soon, the wireless power receiver may have a low reference quality factorvalue—in case a foreign object exists, since the difference between thereference quality factor value and the measured quality factor value issmall (or insignificant), a problem may occur in that the presence ofthe foreign object cannot be easily determined. Accordingly, in thiscase, other determination factors should be further considered, or thepresent or absence of a foreign object should be determined by usinganother method.

According to another exemplary embodiment of the present disclosure, incase an object is sensed (or detected) in the selection phase (510), inorder to determine whether or not a foreign object exists in thecharging area along with the wireless power receiver, the wireless powertransmitter may measure the quality factor value within a specificfrequency area (e.g., operation frequency area). In the coil that isprovided in the wireless power transmitter, inductance and/or componentsof the series resistance may be reduced due to a change in theenvironment, and, due to such decrease, the resonance frequency of thecoil of the wireless power transmitter may be changed (or shifted). Morespecifically, a quality factor peak frequency that corresponds to afrequency in which a maximum quality factor value is measured within theoperation frequency band may be moved (or shifted).

In the ping phase (520), if the wireless power transmitter detects thepresence of an object, the transmitter activates (or Wakes up) areceiver and transmits a digital ping for identifying whether or not thedetected object corresponds to the wireless power receiver. During theping phase (520), if the wireless power transmitter fails to receive aresponse signal for the digital ping—e.g., a signal intensitypacket—from the receiver, the process may be shifted back to theselection phase (510). Additionally, in the ping phase (520), if thewireless power transmitter receives a signal indicating the completionof the power transfer—e.g., charging complete packet—from the receiver,the process may be shifted back to the selection phase (510).

If the ping phase (520) is completed, the wireless power transmitter mayshift to the identification and configuration phase (530) foridentifying the receiver and for collecting configuration and statusinformation.

In the identification and configuration phase (530), if the wirelesspower transmitter receives an unwanted packet (i.e., unexpected packet),or if the wireless power transmitter fails to receive a packet during apredetermined period of time (i.e., out of time), or if a packettransmission error occurs (i.e., transmission error), or if a powertransfer contract is not configured (i.e., no power transfer contract),the wireless power transmitter may shift to the selection phase (510).

The wireless power transmitter may confirm (or verify) whether or notits entry to the negotiation phase (540) is needed based on aNegotiation field value of the configuration packet, which is receivedduring the identification and configuration phase (530). Based on theverified result, in case a negotiation is needed, the wireless powertransmitter enters the negotiation phase (540) and may then perform apredetermined FOD detection procedure. Conversely, in case a negotiationis not needed, the wireless power transmitter may immediately enter thepower transfer phase (560).

In the negotiation phase (540), the wireless power transmitter mayreceive a Foreign Object Detection (FOD) status packet that includes areference quality factor value. Or, the wireless power transmitter mayreceive an FOD status packet that includes a reference peak frequencyvalue. Alternatively, the wireless power transmitter may receive astatus packet that includes a reference quality factor value and areference peak frequency value. At this point, the wireless powertransmitter may determine a quality coefficient threshold value for FOdetection based on the reference quality factor value. The wirelesspower transmitter may determine a peak frequency threshold value for FOdetection based on the reference peak frequency value.

The wireless power transmitter may detect the presence or absence of anFO in the charging area by using the determined quality coefficientthreshold value for FO detection and the currently measured qualityfactor value (i.e., the quality factor value that was measured beforethe ping phase), and, then, the wireless power transmitter may controlthe transmitted power in accordance with the FO detection result. Forexample, in case the FO is detected, the power transfer may be stopped.However, the present disclosure will not be limited only to this.

The wireless power transmitter may detect the presence or absence of anFO in the charging area by using the determined peak frequency thresholdvalue for FO detection and the currently measured peak frequency value(i.e., the peak frequency value that was measured before the pingphase), and, then, the wireless power transmitter may control thetransmitted power in accordance with the FO detection result. Forexample, in case the FO is detected, the power transfer may be stopped.However, the present disclosure will not be limited only to this.

In case the FO is detected, the wireless power transmitter may return tothe selection phase (510). Conversely, in case the FO is not detected,the wireless power transmitter may proceed to the calibration phase(550) and may, then, enter the power transfer phase (560). Morespecifically, in case the FO is not detected, the wireless powertransmitter may determine the intensity of the received power that isreceived by the receiving end during the calibration phase (550) and maymeasure power loss in the receiving end and the transmitting end inorder to determine the intensity of the power that is transmitted fromthe transmitting end. In other words, during the calibration phase(550), the wireless power transmitter may estimate the power loss basedon a difference between the transmitted power of the transmitting endand the received power of the receiving end. The wireless powertransmitter according to the exemplary embodiment of the presentdisclosure may calibrate the threshold value for the FOD detection byapplying the estimated power loss.

In the power transfer phase (560), in case the wireless powertransmitter receives an unwanted packet (i.e., unexpected packet), or incase the wireless power transmitter fails to receive a packet during apredetermined period of time (i.e., time-out), or in case a violation ofa predetermined power transfer contract occurs (i.e., power transfercontract violation), or in case charging is completed, the wirelesspower transmitter may shift to the selection phase (510).

Additionally, in the power transfer phase (560), in case the wirelesspower transmitter is required to reconfigure the power transfer contractin accordance with a status change in the wireless power transmitter,the wireless power transmitter may shift to the renegotiation phase(570). At this point, if the renegotiation is successfully completed,the wireless power transmitter may return to the power transfer phase(560).

In this embodiment, the calibration step 550 and the power transferphase 560 are divided into separate steps, but the calibration step 550may be integrated into the power transfer phase 560. In this case,operations in the calibration step 550 may be performed in the powertransfer phase 560.

The above-described power transfer contract may be configured based onthe status and characteristic information of the wireless powertransmitter and receiver. For example, the wireless power transmitterstatus information may include information on a maximum amount oftransmittable power, information on a maximum number of receivers thatmay be accommodated, and so on. And, the receiver status information mayinclude information on the required power, and so on.

FIG. 6 shows a power control method according to an exemplary embodimentof the present disclosure.

As shown in FIG. 6 , in the power transfer phase (560), by alternatingthe power transfer and/or reception and communication, the wirelesspower transmitter (100) and the wireless power receiver (200) maycontrol the amount (or size) of the power that is being transferred. Thewireless power transmitter and the wireless power receiver operate at aspecific control point. The control point indicates a combination of thevoltage and the electric current that are provided from the output ofthe wireless power receiver, when the power transfer is performed.

More specifically, the wireless power receiver selects a desired controlpoint, a desired output current/voltage, a temperature at a specificlocation of the mobile device, and so on, and additionally determines anactual control point at which the receiver is currently operating. Thewireless power receiver calculates a control error value by using thedesired control point and the actual control point, and, then, thewireless power receiver may transmit the calculated control error valueto the wireless power transmitter as a control error packet.

Also, the wireless power transmitter may configure/control a newoperating point —amplitude, frequency, and duty cycle—by using thereceived control error packet, so as to control the power transfer.Therefore, the control error packet may be transmitted/received at aconstant time interval during the power transfer phase, and, accordingto the exemplary embodiment, in case the wireless power receiverattempts to reduce the electric current of the wireless powertransmitter, the wireless power receiver may transmit the control errorpacket by setting the control error value to a negative number. And, incase the wireless power receiver intends to increase the electriccurrent of the wireless power transmitter, the wireless power receivertransmit the control error packet by setting the control error value toa positive number. During the induction mode, by transmitting thecontrol error packet to the wireless power transmitter as describedabove, the wireless power receiver may control the power transfer.

In the resonance mode, which will hereinafter be described in detail,the device may be operated by using a method that is different from theinduction mode. In the resonance mode, one wireless power transmittershould be capable of serving a plurality of wireless power receivers atthe same time. However, in case of controlling the power transfer justas in the induction mode, since the power that is being transferred iscontrolled by a communication that is established with one wirelesspower receiver, it may be difficult to control the power transfer ofadditional wireless power receivers. Therefore, in the resonance modeaccording to the present disclosure, a method of controlling the amountof power that is being received by having the wireless power transmittercommonly transfer (or transmit) the basic power and by having thewireless power receiver control its own resonance frequency.Nevertheless, even during the operation of the resonance mode, themethod described above in FIG. 6 will not be completely excluded. And,additional control of the transmitted power may be performed by usingthe method of FIG. 6 .

FIG. 7 is a block diagram of a wireless power transmitter according toanother exemplary embodiment of the present disclosure. This may belongto a wireless power transfer system that is being operated in themagnetic resonance mode or the shared mode. The shared mode may refer toa mode performing a several-for-one (or one-to-many) communication andcharging between the wireless power transmitter and the wireless powerreceiver. The shared mode may be implemented as a magnetic inductionmethod or a resonance method.

Referring to FIG. 7 , the wireless power transmitter (700) may includeat least one of a cover (720) covering a coil assembly, a power adapter(730) supplying power to the power transmitter (740), a powertransmitter (740) transmitting wireless power, and a user interface(750) providing information related to power transfer processing andother related information. Most particularly, the user interface (750)may be optionally included or may be included as another user interface(750) of the wireless power transmitter (700).

The power transmitter (740) may include at least one of a coil assembly(760), an impedance matching circuit (770), an inverter (780), acommunication unit (790), and a control unit (710).

The coil assembly (760) includes at least one primary coil generating amagnetic field. And, the coil assembly (760) may also be referred to asa coil cell.

The impedance matching circuit (770) may provide impedance matchingbetween the inverter and the primary coil(s). The impedance matchingcircuit (770) may generate resonance from a suitable frequency thatboosts the electric current of the primary coil(s). In a multi-coilpower transmitter (740), the impedance matching circuit may additionallyinclude a multiplex that routes signals from the inverter to a subset ofthe primary coils. The impedance matching circuit may also be referredto as a tank circuit.

The impedance matching circuit (770) may include a capacitor, aninductor, and a switching device that switches the connection betweenthe capacitor and the inductor. The impedance matching may be performedby detecting a reflective wave of the wireless power that is beingtransferred (or transmitted) through the coil assembly (760) and byswitching the switching device based on the detected reflective wave,thereby adjusting the connection status of the capacitor or the inductoror adjusting the capacitance of the capacitor or adjusting theinductance of the inductor. In some cases, the impedance matching may becarried out even though the impedance matching circuit (770) is omitted.This specification also includes an exemplary embodiment of the wirelesspower transmitter (700), wherein the impedance matching circuit (770) isomitted.

The inverter (780) may convert a DC input to an AC signal. The inverter(780) may be operated as a half-bridge inverter or a full-bridgeinverter in order to generate a pulse wave and a duty cycle of anadjustable frequency. Additionally, the inverter may include a pluralityof stages in order to adjust input voltage levels.

The communication unit (790) may perform communication with the powerreceiver. The power receiver performs load modulation in order tocommunicate requests and information corresponding to the powertransmitter. Therefore, the power transmitter (740) may use thecommunication unit (790) so as to monitor the amplitude and/or phase ofthe electric current and/or voltage of the primary coil in order todemodulate the data being transmitted from the power receiver.

Additionally, the power transmitter (740) may control the output powerto that the data may be transferred through the communication unit (790)by using a Frequency Shift Keying (FSK) method, and so on.

The control unit (710) may control communication and power transfer (ordelivery) of the power transmitter (740). The control unit (710) maycontrol the power transfer by adjusting the above-described operatingpoint. The operating point may be determined by, for example, at leastany one of the operation frequency, the duty cycle, and the inputvoltage.

The communication unit (790) and the control unit (710) may each beprovided as a separate unit/device/chipset or may be collectivelyprovided as one unit/device/chipset.

FIG. 8 shows a wireless power receiver according to another exemplaryembodiment of the present disclosure. This may belong to a wirelesspower transfer system that is being operated in the magnetic resonancemode or the shared mode.

Referring to FIG. 8 , the wireless power receiver (800) may include atleast one of a user interface (820) providing information related topower transfer processing and other related information, a powerreceiver (830) receiving wireless power, a load circuit (840), and abase (850) supporting and covering the coil assembly. Most particularly,the user interface (820) may be optionally included or may be includedas another user interface (820) of the wireless power receiver (800).

The power receiver (830) may include at least one of a power converter(860), an impedance matching circuit (870), a coil assembly (880), acommunication unit (890), and a control unit (810).

The power converter (860) may convert the AC power that is received fromthe secondary coil to a voltage and electric current that are suitablefor the load circuit. According to an exemplary embodiment, the powerconverter (860) may include a rectifier. The rectifier may rectify thereceived wireless power and may convert the power from an alternatingcurrent (AC) to a direct current (DC). The rectifier may convert thealternating current to the direct current by using a diode or atransistor, and, then, the rectifier may smooth the converted current byusing the capacitor and resistance. Herein, a full-wave rectifier, ahalf-wave rectifier, a voltage multiplier, and so on, that areimplemented as a bridge circuit may be used as the rectifier.Additionally, the power converter may adapt a reflected impedance of thepower receiver.

The impedance matching circuit (870) may provide impedance matchingbetween a combination of the power converter (860) and the load circuit(840) and the secondary coil. According to an exemplary embodiment, theimpedance matching circuit may generate a resonance of approximately 100kHz, which may reinforce the power transfer. The impedance matchingcircuit (870) may include a capacitor, an inductor, and a switchingdevice that switches the combination of the capacitor and the inductor.The impedance matching may be performed by controlling the switchingdevice of the circuit that configured the impedance matching circuit(870) based on the voltage value, electric current value, power value,frequency value, and so on, of the wireless power that is beingreceived. In some cases, the impedance matching may be carried out eventhough the impedance matching circuit (870) is omitted. Thisspecification also includes an exemplary embodiment of the wirelesspower receiver (200), wherein the impedance matching circuit (870) isomitted.

The coil assembly (880) includes at least one secondary coil, and,optionally, the coil assembly (880) may further include an elementshielding the metallic part of the receiver from the magnetic field.

The communication unit (890) may perform load modulation in order tocommunicate requests and other information to the power transmitter.

For this, the power receiver (830) may perform switching of theresistance or capacitor so as to change the reflected impedance.

The control unit (810) may control the received power. For this, thecontrol unit (810) may determine/calculate a difference between anactual operating point and a target operating point of the powerreceiver (830). Thereafter, by performing a request for adjusting thereflected impedance of the power transmitter and/or for adjusting anoperating point of the power transmitter, the difference between theactual operating point and the target operating point may beadjusted/reduced. In case of minimizing this difference, an optimalpower reception may be performed.

The communication unit (890) and the control unit (810) may each beprovided as a separate device/chipset or may be collectively provided asone device/chipset.

As described in FIG. 5 etc., the wireless power transmitter and thewireless power receiver go through a Ping Phase and a ConfigurationPhase to enter the Negotiation Phase, or may go through a ping phase, aconfiguration phase, and a negotiation phase to enter a power transferphase and then to a re-negotiation phase.

FIG. 9 is a flowchart schematically illustrating a protocol of a pingphase according to an embodiment.

Referring to FIG. 9 , in the ping phase, the wireless power transmitter1010 checks whether an object exists in an operating volume bytransmitting an analog ping (S1101). The wireless power transmitter 1010may detect whether an object exists in the working space based on achange in current of a transmission coil or a primary coil.

If it is determined that an object exists in the operating volume byanalog ping, the wireless power transmitter 1010 may perform foreignobject detection (FOD) before power transmission to check whether aforeign object exists in the operating volume (S1102). The wirelesspower transmitter 1010 may perform an operation for protecting the NFCcard and/or the RFID tag.

Thereafter, the wireless power transmitter 1010 identifies the wirelesspower receiver 1020 by transmitting a digital ping (S1103). The wirelesspower receiver 1020 recognizes the wireless power transmitter 1010 byreceiving the digital ping.

The wireless power receiver 1020 that has received the digital pingtransmits a signal strength data packet (SIG) to the wireless powertransmitter 1010 (S1104).

The wireless power transmitter 1010 receiving the SIG from the wirelesspower receiver 1020 may identify that the wireless power receiver 1020is located in the operating volume.

FIG. 10 is a flowchart schematically illustrating a protocol of aconfiguration phase according to an embodiment.

In the configuration phase (or identification and configuration phase),the wireless power receiver 1020 transmits its identificationinformation to the wireless power transmitter 1010, the wireless powerreceiver 1020 and the wireless power transmitter 1010 may establish abaseline Power Transfer Contract.

Referring to FIG. 10 , in the configuration phase, the wireless powerreceiver 1020 may transmit an identification data packet (ID) to thewireless power transmitter 1010 to identify itself (S1201). In addition,the wireless power receiver 1020 may transmit an XID (ExtendedIdentification data packet) to the wireless power transmitter 1010(S1202). In addition, the wireless power receiver 1020 may transmit apower control hold-off data packet (PCH) to the wireless powertransmitter 1010 for a power transfer contract (S1203). In addition, thewireless power receiver 1020 may transmit a configuration data packet(CFG) to the wireless power transmitter (S1204).

In accordance with the Extended Protocol for EPP, the wireless powertransmitter 1010 may transmit an ACK in response to the CFG (S1205).

FIG. 11 is a diagram illustrating a message field of a configurationpacket (CFG) of a wireless power receiver according to an embodiment.

A configuration packet (CFG) according to an embodiment may have aheader value of 0x51 and may include a message field of 5 bytes,referring to FIG. 11 .

Referring to FIG. 11 , the message field of the configuration packet CFGmay include a 1-bit authentication (AI) flag, and a 1-bit out-of-band(OB) flag.

The authentication flag AI indicates whether the wireless power receiver1020 supports the authentication function. For example, if the value ofthe authentication flag AI is ‘1’, it indicates that the wireless powerreceiver 1020 supports an authentication function or operates as anauthentication initiator, if the value of the authentication flag AI is‘0’, it may indicate that the wireless power receiver 1020 does notsupport an authentication function or cannot operate as anauthentication initiator.

The out-band (OB) flag indicates whether the wireless power receiver1020 supports out-band communication. For example, if the value of theout-band (OB) flag is ‘1’, the wireless power receiver 1020 instructsout-band communication, if the value of the out-band (OB) flag is ‘0’,it may indicate that the wireless power receiver 1020 does not supportout-band communication.

In the configuration phase, the wireless power transmitter 1010 mayreceive the configuration packet (CFG) of the wireless power receiver1020 and check whether the wireless power receiver 1020 supports anauthentication function and supports out-of-band communication.

FIG. 12 is a flowchart schematically illustrating a protocol of anegotiation step or a renegotiation step according to an embodiment.

In the negotiation phase or renegotiation phase, the power transfercontract related to the reception/transmission of wireless power betweenthe wireless power receiver and the wireless power transmitter isexpanded or changed, or a renewal of the power transfer contract is madethat adjusts at least some of the elements of the power transfercontract, or exchange of information for establishing out-bandcommunication may be performed.

Referring to FIG. 12 , in the negotiation phase, the wireless powerreceiver 1020 may receive an identification data packet (ID) and acapabilities data packet (CAP) of the wireless power transmitter 1010using a general request data packet (GRQ).

The general request packet (GRQ) may have a header value of 0x07 and mayinclude a 1-byte message field. The message field of the general requestpacket (GRQ) may include a header value of a data packet that thewireless power receiver 1020 requests from the wireless powertransmitter 1010 using the GRQ packet. For example, when the wirelesspower receiver 1020 requests an ID packet of the wireless powertransmitter 1010 using a GRQ packet, the wireless power receiver 1020transmits a general request packet (GRQ/id) including a header value(0x30) of the ID packet of the wireless power transmitter 1010 in themessage field of the general request packet (GRQ).

Referring to FIG. 12 , in the negotiation phase or renegotiation phase,the wireless power receiver 1020 may transmit a GRQ packet (GRQ/id)requesting the ID packet of the wireless power transmitter 1010 to thewireless power transmitter 1010 (S1301).

The wireless power transmitter 1010 receiving the GRQ/id may transmitthe ID packet to the wireless power receiver 1020 (S1302). The ID packetof the wireless power transmitter 1010 includes information on theManufacturer Code. The ID packet including information on theManufacturer Code allows the manufacturer of the wireless powertransmitter 1010 to be identified.

Referring to FIG. 12 , in the negotiation phase or renegotiation phase,the wireless power receiver 1020 may transmit a GRQ packet (GRQ/cap)requesting a capability packet (CAP) of the wireless power transmitter1010 to the wireless power transmitter 1010 (S1303). The message fieldof the GRQ/cap may include a header value (0x31) of the capabilitypacket (CAP).

The wireless power transmitter 1010 receiving the GRQ/cap may transmit acapability packet (CAP) to the wireless power receiver 1020 (S1304).

FIG. 13 is a diagram illustrating a message field of a capability packet(CAP) of a wireless power transmitter according to an embodiment.

A capability packet (CAP) according to an embodiment may have a headervalue of 0x31, and referring to FIG. 13 , may include a message field of3 bytes.

Referring to FIG. 13 , a 1-bit authentication (AR) flag and a 1-bitout-of-band (OB) flag may be included in the message field of thecapability packet (CAP).

The authentication flag AR indicates whether the wireless powertransmitter 1010 supports the authentication function. For example, ifthe value of the authentication flag AR is ‘T’, it indicates that thewireless power transmitter 1010 supports an authentication function orcan operate as an authentication responder, if the value of theauthentication flag AR is ‘0’, it may indicate that the wireless powertransmitter 1010 does not support the authentication function or cannotoperate as an authentication responder.

The out-band (OB) flag indicates whether the wireless power transmitter1010 supports out-band communication. For example, if the value of theout-band (OB) flag is ‘1’, the wireless power transmitter 1010 instructsout-band communication, if the value of the out-band (OB) flag is ‘0’,it may indicate that the wireless power transmitter 1010 does notsupport out-band communication.

In the negotiation phase, the wireless power receiver 1020 receives acapability packet (CAP) of the wireless power transmitter 1010, it ispossible to check whether the wireless power transmitter 1010 supportsan authentication function, supports out-of-band communication, and thelike.

And, according to FIG. 12 , in the negotiation phase or re-negotiationphase, the wireless power receiver 1020 may use at least one specificrequest packet (SRQ, Specific Request data packet) to update theelements of the Power Transfer Contract related to the power to beprovided in the power transfer phase, the negotiation phase or there-negotiation phase may be ended (S1305).

The wireless power transmitter 1010 may transmit only ACK, only ACK orNAK, or only ACK or ND in response to the specific request packet SRQaccording to the type of the specific request packet SRQ (S1306).

In the above-described ping phase, configuration phase, andnegotiation/renegotiation phase, a data packet or message exchangedbetween the wireless power transmitter 1010 and the wireless powerreceiver 1020 may be transmitted/received through in-band communication.

FIG. 14 is a flowchart schematically illustrating a protocol of a powertransmission step according to an embodiment.

In the power transfer phase, the wireless power transmitter 1010 and thewireless power receiver 1020 may transmit/receive wireless power basedon a power transfer contract.

Referring to FIG. 14 , in the power transfer phase, the wireless powerreceiver 1020 transmits a control error data packet (CE) includinginformation on the difference between the actual operating point and thetarget operating point to the wireless power transmitter 1010 (S1401).

Also, in the power transfer phase, the wireless power receiver 1020transmits a received power packet (RP, Received Power data packet)including information on the received power value of the wireless powerreceived from the wireless power transmitter 1010 to the wireless powertransmitter 1010 (S1402).

In the power transfer phase, the control error packet (CE) and thereceived power packet (RP) are data packets that are repeatedlytransmitted/received according to timing constraints required forwireless power control.

The wireless power transmitter 1010 may control the level of wirelesspower transmitted based on the control error packet (CE) and thereceived power packet (RP) received from the wireless power receiver1020.

The wireless power transmitter 1010 may respond with an 8-bit bitpattern such as ACK, NAK, ATN, etc. to the received power packet (RP)(S1403).

For a received power packet (RP/0) with a mode value of 0, when thewireless power transmitter 1010 responds with ACK, it means that powertransmission can continue at the current level.

For a received power packet (RP/0) with a mode value of 0, when thewireless power transmitter 1010 responds with NAK, it means that thewireless power receiver 1020 should reduce power consumption.

For a received power packet (RP/l or RP/2) having a mode value of 1 or2, when the wireless power transmitter 1010 responds with ACK, it meansthat the wireless power receiver 1020 has accepted the power correctionvalue included in the received power packet (RP/1 or RP/2).

For a received power packet (RP/1 or RP/2) having a mode value of 1 or2, when the wireless power transmitter 1010 responds with NAK, it meansthat the wireless power receiver 1020 does not accept the powercorrection value included in the received power packet RP/1 or RP/2.

About Receive Power Packet (RP), when the wireless power transmitter1010 responds with ATN, it means that the wireless power transmitter1010 requests permission for communication.

The wireless power transmitter (1010) and the wireless power receiver(1020) can control the transmitted/received power level based on acontrol error packet (CE), a received power packet (RP), and a responseto the received power packet (RP).

Also, in the power transfer phase, the wireless power receiver 1020transmits a charge status data packet (CHS) including information on thecharge state of the battery to the wireless power transmitter 1010(S1404). The wireless power transmitter 1010 may control the power levelof the wireless power based on the information on the state of charge ofthe battery included in the state of charge packet (CHS).

Meanwhile, in the power transfer phase, the wireless power transmitter1010 and/or the wireless power receiver 1020 may enter a renegotiationphase to renew the power transfer contract.

In the power transfer phase, when the wireless power transmitter 1010wants to enter the renegotiation phase, the wireless power transmitter1010 responds to the received power packet (RP) with ATN. In this case,the wireless power receiver 1020 may transmit a DSR/poll packet to thewireless power transmitter 1010 to give the wireless power transmitter1010 an opportunity to transmit a data packet (S1405).

When the wireless power transmitter 1010 transmits a performance packet(CAP) to the wireless power receiver 1020 in response to the DSR/pollpacket (S1406), the wireless power receiver 1020 transmits arenegotiation packet (NEGO) requesting the progress of there-negotiation phase to the wireless power transmitter 1010 (S1407),when the wireless power transmitter 1010 responds with an ACK to therenegotiation packet (NEGO) (S1408), the wireless power transmitter 1010and the wireless power receiver 1020 enter a re-negotiation phase.

In the power transfer phase, when the wireless power receiver 1020 wantsto enter the re-negotiation phase, the wireless power receiver 1020transmits a renegotiation packet (NEGO) requesting the progress of there-negotiation phase to the wireless power transmitter 1010 (S1407),when the wireless power transmitter 1010 responds with an ACK to therenegotiation packet (NEGO) (S1408), the wireless power transmitter 1010and the wireless power receiver 1020 enter a re-negotiation phase.

Hereinafter, a foreign object detection method during power transferwill be described.

When a wireless power transmitter transmits wireless power to a wirelesspower receiver using a magnetic field, if a foreign object exists aroundthe wireless power transmitter, some of the magnetic field is absorbedby the foreign object. Accordingly, some of the wireless powertransmitted by the wireless power transmitter is absorbed by the foreignobject, and the rest is supplied to the wireless power receiver.

From the viewpoint of power transmission efficiency, transmission powerloss occurs as much as the power or energy absorbed by the foreignobject. In this way, since a causal relationship can be establishedbetween the existence of a foreign object and power loss (Ploss), thewireless power transmitter can detect a foreign object through how muchpower loss occurs.

In particular, various methods can be used as a foreign object detectionmethod during power transmission, a method of stopping powertransmission for a short period of time and performing foreign objectdetection within a short period of time during which power transmissionis stopped may be used. The short time during which power transmissionis stopped can be referred to as slot time, a method of stopping powertransmission during the slot time and detecting a foreign object may bereferred to as foreign object detection using a slot, Slotted FOD, orSlot FOD. Hereinafter, it is collectively referred to as Slotted FOD.

Since the slotted FOD stops power transmission for a short time, thewireless power reception can be continuously maintained without a largereduction in the rectified voltage of the wireless power receiver duringthe time of detecting the foreign object, since it does not affect theoperation of the wireless power receiver, there is an advantage that theoperation of the wireless power receiver can be continuously maintained.

Among Slotted FODs, in the power transfer phase, there is a Slotted QFOD in which a wireless power transmitter stops power transmission for ashort time and detects a foreign object from a change in current and/orvoltage that is naturally reduced in a resonant circuit including aprimary coil.

FIG. 15 is a schematic circuit diagram of a wireless power transmittersupporting a foreign object detection method by Slotted Q FOD, and FIG.16 is a graph schematically showing a voltage attenuation waveform of aprimary coil during a slot time.

Referring to FIG. 15 , the power conversion circuit of the wirelesspower transmitter may be outlined as an LC circuit including a fullbridge inverter including four switches H1, H2, L1, and L2.

In the power transfer phase, the wireless power transmitter receivespower from a power supply source expressed as an input voltage andprovides wireless power to the wireless power receiver through theprimary coil Lp. At this time, the four switches (H1, H2, L1, L2) of thefull bridge inverter are controlled to form a circuit consisting of aninput voltage—a capacitor (Cp)—a primary coil (Lp). Referring to FIG. 16, a sine wave voltage having a substantially constant peak value may beapplied to the primary coil Lp in the power transfer phase.

When forming a slot time for foreign object detection, the full bridgeinverter has H1 and H2 switches open, when the L1 and L2 switches areswitched to the closed state, the wireless power transmitter forms aclosed-loop resonant circuit consisting of a capacitor (Cp) and aprimary coil (Lp), the supply of power to the resonant circuit is cutoff.

Referring to FIG. 16 , during the slot time, the voltage (or current) ofthe primary coil Lp oscillates in a waveform having a resonant frequencyaccording to the capacitance of the capacitor Cp and the inductancecharacteristics of the primary coil Lp, it is gradually attenuated bythe resistance affecting the resonant circuit. The quality factor (Qfactor) of the LC resonant circuit can be measured from the dampingratio (or damping coefficient) of the voltage (or current). And, if aforeign object adjacent to the wireless power transmission deviceexists, since the Q factor is generally measured lower, the presence ofa foreign object can be determined from the Q factor measured within theslot time or the voltage (or current) waveform of the primary coil Lpmeasured within the slot time.

As described above, the foreign object detection method by Slotted Q FODis a method of cutting off external power during the slot time, forminga resonance circuit including a primary coil, measuring a Q factor froma voltage (or current) waveform of the primary coil Lp during a slottime, and detecting the presence of a foreign object based on this.

However, in the power transfer phase, the current flowing through theprimary coil Lp and the voltage applied to the primary coil Lpcontinuously change with time as a sine wave. Therefore, according tothe start time of the slot time, the current flowing through the primarycoil Lp and the voltage applied to the primary coil Lp may vary, thisresults in a voltage waveform or current waveform of the primary coil(Lp) stage being different each time during the slot time. In addition,since the Q factor measured depending on the voltage waveform or currentwaveform of the primary coil (Lp) stage is also inconsistent,reliability of foreign object detection results by Slotted Q FOD may beweakened.

Hereinafter, a method for more accurately measuring a Q factor measuredwithin a slot time and a foreign object detection method using the samewill be described.

FIG. 17 is a flowchart illustrating a foreign object detection methodaccording to an embodiment.

Referring to FIG. 17 , when the Slotted Q FOD starts (S1501), thecommunication/control circuit of the wireless power transmitter detectsthe time when the current of the primary coil (Lp) becomes 0 (S1502).

The time point at which the current in the primary coil (Lp) becomeszero may be a time point when the value of the AC current flowing in theprimary coil Lp is converted from a positive value to a negative valueor a time point when the value is converted from a negative value to apositive value.

If the wireless power transmitter includes a configuration capable ofmonitoring the current value of the primary coil (Lp), thecommunication/control circuit of the wireless power transmitter canreceive the current value of the primary coil (Lp) from the aboveconfiguration and can easily detect the point in time when the currentof the primary coil (Lp) becomes zero.

However, if the wireless power transmitter does not have a configurationcapable of monitoring the current value of the primary coil (Lp), thecommunication/control circuit of the wireless power transmission devicemay detect a time point having a phase difference of 90 degrees from thetime point at which the voltage value of the primary coil Lp becomes 0as the time point at which the current in the primary coil Lp becomes 0.This is because the voltage and current of the primary coil Lp have aphase difference of 90 degrees.

The communication/control circuit of the wireless power transmitter cutsoff power transmitted to the primary coil Lp in the power transfer phasewhen the current of the primary coil Lp becomes zero (S1503). Forexample, as described with reference to FIG. 15 , thecommunication/control circuit controls the four switches (H1, H2, L1,L2) of the full bridge inverter, constitutes a closed-loop resonantcircuit composed of a capacitor Cp—the primary coil Lp and can cut offpower transmitted to the primary coil Lp. Or, for example, controllingthe power transmitted to the primary coil Lp in the power transfer phaseto be OFF, a closed-loop resonant circuit composed of a capacitor Cp anda primary coil Lp may be configured to block power transmitted to theprimary coil Lp.

When the power transmitted to the primary coil (Lp) is cut off in thepower transfer phase, the slot time starts. Therefore, the slot timestarts at the time when the current of the primary coil Lp becomes zero.According to this embodiment, since the starting point of the slot timefor the Slotted Q FOD is maintained at the point at which the current ofthe primary coil Lp becomes 0, a more consistent and reliable Q factorcan be obtained.

The communication/control circuit of the wireless power transmitteracquires data on the voltage value across the primary coil (Lp) or thecurrent value flowing through the primary coil (Lp) during the slot time(S1504).

FIG. 18 is a diagram showing an example of data acquired in step S1504.

Referring to FIG. 18 , the communication/control circuit of the wirelesspower transmitter records the voltage value across the primary coil Lpor the current value flowing through the primary coil Lp at varioustimes within the slot time.

Thereafter, the communication/control circuit of the wireless powertransmitter detects peak values of the voltage value or current value ofthe primary coil (Lp) within the slot time based on the data obtained instep S1504 (S1505).

Referring to FIG. 18 , the communication/control circuit of the wirelesspower transmitter may detect peak values (P₁, P₂, P₃, . . . , P_(n)) ofthe attenuation waveform based on the values of the data obtained instep S1504.

Thereafter, the communication/control circuit of the wireless powertransmitter may perform regression analysis based on the peak valuesdetected in step S1505 (S1506).

However, the communication/control circuit of the wireless powertransmitter may obtain effective peak values to be subjected toregression analysis among the peak values detected in step S1505.

FIG. 19 is a diagram for explaining a method of obtaining effective peakvalues according to an exemplary embodiment.

Referring to FIG. 19 , among the detected peak values (P₁, P₂, P₃, . . .P_(n)) the communication/control circuit of the wireless powertransmitter may obtain effective peak values excluding the peak valuesP₁ and P₂ of the initial period S₁.

Theoretically, since the peak values detected within the slot time arevalues measured in the RLC resonance circuit, they should form aspecific exponential function, peak values derived from variousexperiments generally have an exponential trend, but it is not definedas a single exponential function. In particular, among the peak valuesdetected within the slot time, the peak value of the initial section(S₁) tended to adversely affect the regression analysis result. It ispresumed that after the resonance circuit is configured, otherinfluences other than the characteristics of the resonance circuit areinitially applied to the voltage value or current value of the primarycoil Lp in a transient state.

Thus, in this embodiment, among the detected peak values (P₁, P₂, P₃, .. . , P_(n)), a method of obtaining effective peak values excluding thepeak values P₁ and P₂ of the initial period S₁ is proposed.

The length of the initial section S₁ may be determined differentlyaccording to embodiments. For example, only the first peak value P₁ maybe included in the initial period S₁, or two or more first peak valuesmay be included.

In addition, among the detected peak values (P₁, P₂, P₃, . . . , P_(n)),the communication/control circuit of the wireless power transmitter mayobtain an effective peak value except for the peak value P₄ of thelatter period S₃.

The second half section (S₃) may be a section in which the deviation ofthe peak values (P₄) is less than a certain level. Alternatively, thesecond half section S₃ may be a section in which the peak values P₄ havevalues substantially close to zero.

Since the peak values (P₄) of the latter period (S₃) may also act asfactors that adversely affect the regression analysis result, in thisembodiment, a method of obtaining an effective peak value excluding thepeak value P₄ of the second half section S₃ among the detected peakvalues P₁, P₂, P₃, . . . , P_(n) is proposed.

Alternatively, the second half section S₃ may be determined according tothe number of acquired valid peak values. For example, when 15 arepredetermined as the number of valid peak values for regressionanalysis, a section in which peak values exist after 15 valid peakvalues are obtained may be a second half section S₃.

Meanwhile, for continuity of providing wireless power to the wirelesspower receiver, the slot time is preferably formed within 100 μs. Inorder to reduce the slot time as much as possible, after a preset numberof effective peak values are obtained, the slot time is ended andwireless power transmission may be resumed.

FIG. 20 is a diagram for explaining a regression analysis methodaccording to an embodiment.

The communication/control circuit of the wireless power transmitter mayderive an exponential function that is an envelope of effective peakvalues through regression analysis based on a plurality of effectivepeak values.

FIG. 20 shows an example in which an exponential function ofy=137.79e^(−7236x) is derived based on 9 effective peak values.

When an exponential function, which is an envelope of effective peakvalues, is derived, the communication/control circuit of the wirelesspower transmitter may obtain a Q factor based on the exponentialfunction (S1507).

The exponential function can be expressed as N(t)=N₀e^(−t/π), and in theexponential function shown in FIG. 20 , a time constant (τ) becomes1/7236.

The correlation between the Q factor, the damping ratio (ξ), and thetime constant (τ) can be expressed by the following equation.

$\begin{matrix}{Q = {\frac{1}{\zeta} = {\frac{w_{0}}{2_{\alpha}} = {\frac{\tau w_{0}}{2} = {{\pi\tau}f_{0}}}}}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

When the f0 value is 111000 (Hz), the Q factor value is calculated to beabout 48.17 based on the exponential function of FIG. 20 d.

As such, the communication/control circuit of the wireless powertransmitter may calculate and obtain the value of the Q factor using thetime constant τ of the exponential function derived in step S1506.

The communication/control circuit of the wireless power transmitter maydetect a foreign object between the wireless power transmitter and thewireless power receiver using the acquired Q factor (S1508).

For example, the communication/control circuit of the wireless powertransmitter may compare the Q factor value obtained in step S1507 with apreviously stored Q factor value to estimate the presence of a foreignobject. That is, as the Q factor value acquired in step S1507 is lowerthan the previously stored Q factor value, the possibility of existenceof a foreign object increases. Therefore, the communication/controlcircuit of the wireless power transmitter when the difference betweenthe pre-stored Q factor value and the Q factor value obtained in stepS1507 is greater than the threshold value, it can be determined that aforeign object exists.

The pre-stored Q factor value may be a pre-measured Q factor value inthe absence of a foreign object or a Q factor value received from thewireless power receiver.

The communication/control circuit of the wireless power transmitter maytransmit information (data packet or response pattern) according to thedetection result of the foreign object to the wireless power receiver,and terminate the Slotted Q FOD (S1509).

As described above, according to the present embodiment, in performingSlotted Q FOD, by setting the starting point of the slot time to thepoint at which the current of the primary coil Lp becomes, it enables amore consistent and reliable Q factor to be obtained.

Also, according to this embodiment, in performing Slotted Q FOD, anexponential function, which is the envelope of effective peak values, isderived through regression analysis using a plurality of effective peakvalues, and a Q factor is obtained based on this, it enables morereliable Q factor acquisition.

Also, according to this embodiment, in performing Slotted Q FOD, sincethe effective peak values are selected excluding the peak values of theearly section and/or the latter section among the obtained peak values,it enables more reliable Q factor acquisition.

Meanwhile, in the following description, a method of obtaining areference Q factor value serving as a comparison standard of the Qfactor value obtained when determining the existence possibility of aforeign object in step S1508 will be described.

FIG. 21 is a flowchart for explaining a method of obtaining a referenceQ factor according to an embodiment.

The method for obtaining a reference Q factor described with referenceto FIG. 21 is performed before transmitting wireless power to a wirelesspower receiver, for example, the ping step may be performed in a statein which an object does not exist in the operating volume of thewireless power transmitter, that is, above the primary coil. Therefore,the method of acquiring the reference Q factor according to the presentembodiment may be performed before transmitting a digital ping to thewireless power receiver.

The communication/control circuit of the wireless power transmitterprovides driving power to the primary coil in order to obtain areference Q factor of the wireless power transmitter (S1601).

The driving power may be at least one pulse signal.

After providing at least one pulse signal to the primary coil, thecommunication/control circuit blocks driving power (S1602).

The communication/control circuit may constitute a closed-loop resonantcircuit composed of a capacitor Cp and a primary coil Lp while cuttingoff driving power. For example, as described above with reference toFIG. 15 , the communication/control circuit controls the four switchesH1, H2, L1, and L2 of the full bridge inverter to configure aclosed-loop resonant circuit composed of a capacitor Cp-primary coil Lp.

Due to the applied driving power, in the closed-loop resonant circuitcomposed of capacitor Cp-primary coil Lp, the voltage (or current) ofthe primary coil Lp oscillates in a waveform having a resonant frequencyaccording to the capacitance of the capacitor Cp and the inductancecharacteristics of the primary coil Lp, it is gradually attenuated bythe resistance affecting the resonant circuit.

The communication/control circuit of the wireless power transmitteracquires data on the voltage value across the primary coil (Lp) or thecurrent value flowing through the primary coil (Lp) (S1603).

In the foregoing embodiment, similar to what was described withreference to FIG. 18 , the communication/control circuit of the wirelesspower transmitter records the voltage value across the primary coil (Lp)or the current value flowing through the primary coil (Lp) at variouspoints in time within the slot time.

Thereafter, the communication/control circuit of the wireless powertransmitter detects peak values of the voltage value or current value ofthe primary coil Lp based on the data obtained in step S1603 (S1604).

In the foregoing embodiment, similar to that described with reference toFIG. 18 , the communication/control circuit of the wireless powertransmitter may detect peak values P₁, P₂, P₃, . . . , P_(n) of theattenuation waveform.

Thereafter, the communication/control circuit of the wireless powertransmitter may perform regression analysis based on the peak valuesdetected in step S1604 (S1605).

However, the communication/control circuit of the wireless powertransmitter may obtain effective peak values to be subjected toregression analysis among the peak values detected in step S1604.

In the foregoing embodiment, similarly to that described with referenceto FIG. 19 , among the detected peak values (P₁, P₂, P₃, . . . , P_(n)),the communication/control circuit of the wireless power transmitter mayobtain an effective peak value excluding the peak values P₁ and P₂ ofthe initial period S₁ and/or the peak value P₄ of the second period S₃.Since specific details thereof have been described with reference toFIG. 19 , additional description thereof will be omitted.

The communication/control circuit of the wireless power transmitter mayderive an exponential function that is an envelope of effective peakvalues through regression analysis based on a plurality of effectivepeak values.

When an exponential function, which is an envelope of effective peakvalues, is derived, the communication/control circuit of the wirelesspower transmitter may obtain a reference Q factor based on theexponential function (S1606).

Since the method of calculating the Q factor using the time constant zof the exponential function has been described with reference to FIG. 20and the like, further description thereof will be omitted.

Since the method for obtaining the reference Q factor according to thepresent embodiment uses at least one pulse signal as driving power, itmay be called Impulse Q, and the obtained reference Q factor may becalled Impulse Q factor.

The communication/control circuit of the wireless power transmitter maydetect an operating volume, that is, an object existing above theprimary coil, in the ping phase using the obtained reference Q factor.

For example, the communication/control circuitry of a wireless powertransmitter can estimate the presence of an object existing in theaction space by comparing the obtained reference Q factor with apreviously stored Q factor (a Q factor measured in a state where noobject exists in the action space). That is, as the obtained reference Qfactor value is lower than the pre-stored Q factor value, theprobability of existence of the object increases. Therefore, when thedifference between the pre-stored Q factor value and the reference Qfactor value obtained in step S1606 is greater than the threshold value,the communication/control circuit of the wireless power transmitter maydetermine that an object exists in the operating space.

In addition, by comparing the Q factor obtained through the Slotted QFOD performed in the power transfer phase with the reference Q factorvalue obtained in step S1606, the communication/control circuit of thewireless power transmitter may detect a foreign object existing betweenthe wireless power transmitter and the wireless power receiver.

The wireless power transmitter in the embodiment according to theabove-described FIGS. 9 to 21 corresponds to the wireless powertransmission apparatus or the wireless power transmitter or the powertransmission unit disclosed in FIGS. 1 to 8 . Accordingly, the operationof the wireless power transmitter in this embodiment is implemented byone or the same or more than two combinations of each component of thewireless power transmitter in FIGS. 1 to 8 . For example,reception/transmission of a message or data packet according to FIGS. 9to 21 is included in the operation of the communication/control unit.

The wireless power receiving apparatus in the embodiment according tothe above-described FIGS. 9 to 21 corresponds to the wireless powerreceiving apparatus or the wireless power receiver or the powerreceiving unit disclosed in FIGS. 1 to 8 . Accordingly, the operation ofthe wireless power receiver in this embodiment is implemented by one orthe same or a combination of two or more of the respective components ofthe wireless power receiver in FIGS. 1 to 8 . For example,reception/transmission of a message or data packet according to FIGS. 9to 21 may be included in the operation of the communication/controlunit.

Since all components or steps are not essential for the wireless powertransmission method and apparatus, or the reception apparatus and methodaccording to the embodiment of the present document described above, anapparatus and method for transmitting power wirelessly, or an apparatusand method for receiving power may be performed by including some or allof the above-described components or steps. In addition, theabove-described wireless power transmission apparatus and method, or theembodiment of the reception apparatus and method may be performed incombination with each other. In addition, each of the above-describedcomponents or steps is not necessarily performed in the order described,and it is also possible that the steps described later are performedbefore the steps described earlier.

The above description is merely illustrative of the technical idea ofthe present document, those of ordinary skill in the art to which thepresent document pertains will be able to make various modifications andvariations without departing from the essential characteristics of thepresent document. Accordingly, the embodiments of the present documentdescribed above may be implemented separately or in combination witheach other.

Accordingly, the embodiments disclosed in the present document are notintended to limit the technical spirit of the present document, but toexplain, and the scope of the technical spirit of the present documentis not limited by these embodiments. The protection scope of the presentdocument should be construed by the following claims, all technicalideas within the scope equivalent thereto should be construed as beingincluded in the scope of the present document.

1-20. (canceled)
 21. A wireless power transmitter configured to transmita wireless power to a wireless power receiver, the wireless powertransmitter comprising: a power conversion circuit including a primarycoil for transmitting the wireless power to the wireless power receiver;and a communication/control circuit communicating with the wirelesspower receiver and controlling the power conversion circuit, wherein thecommunication/control circuit is configured to: stop a transmission ofthe wireless power during a slot time for detecting a foreign objectbetween the wireless power receiver and the wireless power transmitter,and detect the foreign object based on a change in voltage or current ofthe primary coil within the slot time, and wherein the slot time startsfrom a time point at which the current of the primary coil becomes zero.22. The wireless power transmitter of claim 21, wherein thecommunication/control circuit is configured to cause the slot time tostart from a time point having a phase difference of 90 degrees from atime point when the voltage of the primary coil becomes zero.
 23. Thewireless power transmitter of claim 21, wherein thecommunication/control circuit is configured to: calculate an envelopebased on peak values of current values or voltage values of the primarycoil within the slot time, and detect the foreign object based on a timeconstant of the envelope.
 24. The wireless power transmitter of claim23, wherein the envelope is calculated based on effective peak valuesobtained excluding peak values of an initial section among the peakvalues.
 25. The wireless power transmitter of claim 24, wherein theeffective peak values are obtained by further excluding peak values of alatter section among the peak values.
 26. The wireless power transmitterof claim 23, wherein the envelope is calculated through regressionanalysis based on the peak values.
 27. The wireless power transmitter ofclaim 23, wherein the communication/control circuit is configured to:calculate a quality factor based on the time constant of the envelope,and detect the foreign object based on the calculated quality factor.28. A method for detecting a foreign object, the method performed by awireless power transmitter, wherein the wireless power transmitterincludes a primary coil for transmitting wireless power to a wirelesspower receiver, the method comprising: supplying power to the primarycoil to provide the wireless power to the wireless power receiver;blocking the power supplied to the primary coil during a slot time; anddetecting the foreign object based on a change in voltage or current ofthe primary coil within the slot time, wherein the slot time starts froma time point at which the current of the primary coil becomes zero. 29.The method of claim 28, wherein the method comprising: causing the slottime to start from a time point having a phase difference of 90 degreesfrom a time point when the voltage of the primary coil becomes zero. 30.The method of claim 28, wherein the method comprising: calculating anenvelope based on peak values of current values or voltage values of theprimary coil within the slot time, and detecting the foreign objectbased on a time constant of the envelope.
 31. The method of claim 30,wherein the envelope is calculated based on effective peak valuesobtained excluding peak values of an initial section among the peakvalues.
 32. The method of claim 31, wherein the effective peak valuesare obtained by further excluding peak values of a latter section amongthe peak values.
 33. The method of claim 30, wherein the envelope iscalculated through regression analysis based on the peak values.
 34. Themethod of claim 30, wherein the method comprising: calculating a qualityfactor based on the time constant of the envelope, and detecting theforeign object based on the calculated quality factor.
 35. A wirelesspower transmitter configured to transmit a wireless power to a wirelesspower receiver, the wireless power transmitter comprising: a powerconversion circuit including a primary coil for transmitting thewireless power to the wireless power receiver; and acommunication/control circuit communicating with the wireless powerreceiver and controlling the power conversion circuit, wherein thecommunication/control circuit is configured to: stop a transmission ofthe wireless power during a slot time for detecting a foreign objectbetween the wireless power receiver and the wireless power transmitter,and detect the foreign object based on a change in voltage or current ofthe primary coil within the slot time, and wherein thecommunication/control circuit is configured to detect the foreign objectbased on the change in effective peak values obtained excluding a peakvalue of an initial section among peak values of current values orvoltage values of the primary coil generated within the slot time. 36.The wireless power transmitter of claim 35, wherein thecommunication/control circuit is configured to: calculate an envelopebased on the effective peak values, and detect the foreign object basedon a time constant of the envelope.
 37. The wireless power transmitterof claim 35, wherein the envelope is calculated through regressionanalysis based on the peak values.
 38. The wireless power transmitter ofclaim 35, wherein the communication/control circuit is configured to:calculate a quality factor based on the time constant of the envelope,and detect the foreign object based on the calculated quality factor.39. The wireless power transmitter of claim 35, wherein the effectivepeak values are obtained by further excluding peak values of a lattersection among the peak values.
 40. The wireless power transmitter ofclaim 35, wherein the slot time starts from a time point at which thecurrent of the primary coil becomes zero.